Background. The ACIP (American Committee on Immunization Practices) has now recommended influenza vaccination for all children 6 months to 18 years of age. While many school-aged children will be vaccinated in the medical home, the large number of children for whom the vaccine is now recommended exceeds the capacity of many primary care settings. Schools have been recommended as potential sites for influenza vaccination, yet little is known about the feasibility, implementation requirements, costs, or effectiveness of school-based influenza vaccination (SIV) programs. This project will implement and rigorously evaluate the feasibility, acceptability, billing and reimbursement components, costs, cost-effectiveness, and overall effectiveness of an SIV program that targets diverse populations and different intensity of interventions.